Analysis of even harmonics generation in an isolated electric power system

Norikazu Kanao*, Yasuhiro Hayashi, Junya Matsuki

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


Harmonics bred from loads are mainly odd order because the current waveforms have half-wave symmetry. Since the even harmonics are negligibly small, they generally are not measured in electric power systems. However, even harmonics were measured at a 500/275/154 kV substation in Hokuriku Electric Power Company after a transmission line fault was corrected. The even harmonics caused malfunctions of protective digital relays because the relays used 4th harmonics at the input filter as the automatic supervisory signal. This paper describes mechanisms of generation of the even harmonics by comparing the measured waveforms with the ATP-EMTP simulation results. Analysis of these results has clearly shown that there are three different mechanisms of generation of even harmonics. The first mechanism is the appearance of a magnetizing current in transformers due to flux deviation by the DC component of the fault current. The second mechanism is harmonic conversion of a synchronous machine which generates even harmonics when the DC component or the even harmonic current flow into the machine. The third mechanism is an increase of harmonic impedance due to an isolated power system, thus producing the harmonic voltages. The design of the input filter of protective digital relays should take into account even harmonics generation in an isolated power system.

Original languageEnglish
Pages (from-to)56-63
Number of pages8
JournalElectrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi)
Issue number2
Publication statusPublished - 2009 Apr 30
Externally publishedYes


  • DC current
  • EMTP
  • Even harmonics
  • Harmonic impedance
  • Magnetizing current
  • Synchronous machine

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering


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